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Further investigation IR below 2 Megohms or 20 Megohms??

RobW

Has the guidance on minimum insulation resistance changed in the new OSG?? I subscribe to the IET electronic versions, the current online IET OSG says that further investigation is required below 20Mohms rather than the previous versions advising further investigation below 2 Megohms? Is this just an electronic typo or has thid guidance changed.

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  • 0

    In my view, a NEW installation should be expected to reach 20 Megohms, unless there is some exceptional reason to expect and accept a lower figure.

    For an EXISTING installation, a much lower figure could be reasonably accepted.

  • 0 in reply to broadgage

    I'd generally moderate that with a bound about the size of installation (well total cable lengths) and cable type.  It is not sensible with MICC if you have  hundreds of metres of it. I know it is not often used, but it still does appear, and is mandated in some types of listed building. But yes, a new run of up to half a km of PVC, 20megs is entirely credible., and will probably spot that back box that got squeezed full of plaster...

    Mike

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  • 0 in reply to broadgage

    I'd generally moderate that with a bound about the size of installation (well total cable lengths) and cable type.  It is not sensible with MICC if you have  hundreds of metres of it. I know it is not often used, but it still does appear, and is mandated in some types of listed building. But yes, a new run of up to half a km of PVC, 20megs is entirely credible., and will probably spot that back box that got squeezed full of plaster...

    Mike

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